dotnet/efcore · error · InvalidOperationException

ObjectCreation: Missing constructor: {objectCreation}

Error message

ObjectCreation: Missing constructor: {objectCreation}

What it means

The constructor symbol resolved, but reflection type.GetConstructor(paramTypes) returned null and the type is not the struct parameterless-constructor case. The constructor is known to Roslyn but not found via reflection, so the translator cannot build the NewExpression with arguments.

Source

Thrown at src/EFCore.Design/Query/Internal/CSharpToLinqTranslator.cs:838

        {
            throw new InvalidOperationException($"ObjectCreation: couldn't find IMethodSymbol for constructor: {objectCreation}");
        }

        Check.DebugAssert(constructorSymbol.MethodKind == MethodKind.Constructor);

        var type = ResolveType(constructorSymbol.ContainingType);

        // Find the reflection constructor that matches the constructor symbol's signature
        var parameterTypes = constructorSymbol.Parameters.Select(ps => ResolveType(ps.Type)).ToArray();
        var constructor = type.GetConstructor(parameterTypes);

        var newExpression = constructor is not null
            ? New(
                constructor,
                objectCreation.ArgumentList?.Arguments.Select(a => Visit(a)) ?? [])
            : parameterTypes.Length == 0 // For structs, there's no actual parameterless constructor
                ? New(type)
                : throw new InvalidOperationException($"ObjectCreation: Missing constructor: {objectCreation}");

        switch (objectCreation.Initializer)
        {
            // No initializers, just return the NewExpression
            case null or { Expressions: [] }:
                return newExpression;

            // Assignment initializer (new Blog { Name = "foo" })
            case { Expressions: [AssignmentExpressionSyntax, ..] }:
                return MemberInit(
                    newExpression,
                    objectCreation.Initializer.Expressions.Select(e =>
                    {
                        if (e is not AssignmentExpressionSyntax { Left: var lValue, Right: var value })
                        {
                            throw new NotSupportedException(
                                $"ObjectCreation: non-assignment initializer expression of type '{e.GetType().Name}': {objectCreation}");
                        }

View on GitHub (pinned to dbf9771522)

Solutions

Make the constructor public
Add [InternalsVisibleTo] for the consuming assembly
Use the parameterless constructor plus property initializers instead
Avoid by-ref constructor parameters in precompiled queries

Example fix

// before
internal Entity(int id) { Id = id; }
// after
public Entity() { }
// usage: new Entity { Id = b.Id }

Defensive patterns

Strategy: validation

Validate before calling

// Confirm the constructor is reflection-discoverable with the exact parameter types.
var ctor = typeof(Entity).GetConstructor(new[] { typeof(int) });
if (ctor is null) { /* make public / add InternalsVisibleTo / drop by-ref params */ }

Prevention

Make constructors used in precompiled queries public, or grant InternalsVisibleTo
Avoid ref/out/in constructor parameters
Use parameterless construction plus property initializers where possible

When it happens

Trigger: A non-public constructor, a constructor with by-ref/out/in parameters or custom modifiers whose reflection signature doesn't match, or a constructor defined in a different assembly version than the runtime load.

Common situations: Internal constructors across assemblies; constructors with in/ref parameters; records or types with non-public constructors; interop types.

Related errors

AI-assisted analysis of dotnet/efcore@dbf9771522 (2026-08-06). Data as JSON: /api/errors/599127f882da6630. Report an issue: GitHub.